The MQ-5 Gas sensor can detect or measure gasses like LPG, natural gas and town gas . The module version of this sensor comes with a Digital Pin which makes this sensor to operate even without a microcontroller and that comes in handy when you are only trying to detect one particular gas. When it comes to measuring the gas in ppm the analog pin has to be used, the analog pin also TTL driven and works on 5V and hence can be used with most common microcontrollers.
The pin connection of MQ5 Gas Sensor to Arduino
Note:The sensor value only reflects the approximated trend of gas concentration in a permissible error range, it DOES NOT represent the exact gas concentration. The detection of certain components in the air usually requires a more precise and costly instrument, which cannot be done with a single gas sensor. If your project is aimed at obtaining the gas concentration at a very precise level, then we do not recommend this gas sensor.
Warranty Period: 12 months
Features
Operating Voltage is +5V
Can be used to detect LPG or Butane gas
Analog output voltage: 0V to 5V
Digital Output Voltage: 0V or 5V (TTL Logic)
Preheat duration 20 seconds
Can be used as a Digital or analog sensor
The Sensitivity of Digital pin can be varied using the potentiometer
Interface MQ-5 Gas Sensor with Arduino ,from www.circuitstoday.com show how to interface the analog and digital output pin of MQ5 gas sensor using Arduino.